Melt-spinning process

ABSTRACT

THIS INVENTION PROVIDES A HIGH-SPEED, MELT-SPINNING PROCESS FOR PRODUCING TEXTILE FIBER HAVING AN IMPROVED RESPONSE TO FALSE-TWIST TEXTURING.

Jan. 5, 1971 TIN YAM AU MELT-SPINNING PROCESS Filed Oct. 16, 1968 INVENTOR Tl N YAM AU ATTORNEY United States Patent Ofiice Patented Jan. 5, 1971 U.S. Cl. 264-210 3 Claims ABSTRACT OF THE DISCLOSURE This invention provides a high-speed, melt-spinning process for producing textile fiber having an improved response to false-twist texturing.

This application is a continuation-in-part of my application Ser. No. 671,832, filed Sept. 29, 1967.

DESCRIPTION OF THE INVENTION Synthetic fibers prepared from polymers of bis(4-aminocyclohexyl)methane, hereafter referred to as PACM, and dodecanedioic acid (PACM-12) representing the diamino. and diacid units respectively are known as described in Belgian Pat. 668,704. As shown therein, such fibers are preferably melt-spun into a nonoxidizing atmosphere to avoid excessive degradation because of the high spinning temperatures involved. The nonoxidizing atmosphere is preferably heated to reduce excessive development of molecular orientation which takes place as the filaments solidify and are pulled away from the spinning orifices. The filaments are then drawn and preferably annealed by heating at a temperature of from about 150 to 180 C.

High-speed spinning processes for producing oriented synthetic fibers are known as shown for example in U.S. 3,053,611. Processes employing even higher spinning speeds are also known. When attempts are made to spin a polymer of PACM-12 by high-speed processes as is desired for commercial operation, fibers having tensile properties equivalent to those prepared at lower spinning speeds are obtained; however, it is found that performance of these fibers in fabrics and under textile processing conditions is inferior to that of the fibers having equivalent tensile properties but spun at lower spinning speeds.

This invention comprises a high-speed, melt-spinning process for producing textile fibers having a tenacity of at least 3.0 g.p.d. and an improved response to textile processing from a polymer consisting essentially of PACM12 units. The PACM employed for polymerization should contain from 45% to 100% of the trans-trans (tt) isomer. Molten polymer having a relative viscosity of at least about 40 is spun at a temperature 290340 C. through a spinneret and the extruded filaments are withdrawn at a speed of at least 1300 y.p.m. such that the tension on the filaments in the spinning and quenching zone is less than about 0.30 g.p.d., preferably 005-- 0.25 g.p.d. The filaments are then drawn from 1.2 to 2.0x. Preferably, the drawn filaments are annealed without stretching at a temperature of 140-180 C.

DESCRIPTION OF DRAWINGS The drawing shows a typical set-up for the high-speed spinning process of the invention. Polymer stream A is extruded through holes of spinneret B. Chamber D represents a diffuser through which steam is passed to blanket the spinneret face. Tail pipe E is a heated conduit that maintains the filaments at elevated temperatures whereby excessive tension build-up is prevented. The filaments are then quenched as by passage through a perforated chimney (not shown) into which air is aspirated and then pass over finish roll F to feed rolls G. The filaments are drawn between feed rolls G and draw rolls H. Some additional draw may be applied between draw rolls H and annealing rolls I, the latter being enclosed by a heated chamber as indicated by broken lines. The filaments are then led to a suitable windup means.

STANDARDS AND CALCULATIONS The expression relative viscosity as used herein signifies the ratio of the flow time in a viscometer of a polymer solution relative to the flow time of the solvent by itself. Measurements of relative viscosities as referred to herein and as measured in the examples is determined from a solution of 3.7 grams of polyamide in 50 ml. of a 1:1 mixture by weight of 98100% formic acid and phenol at 25 C., unless otherwise noted.

Crimp index as shown in the following example is measured on false-twist textured yarns after lagging for 24 hours after texturing on a commercial Superloft (trademark of the Leesona Corp., Warwick, RI.) machine such as the Model Nos. 552 and 553. A false-twist texturing machine running at turns per inch (31.5/cm.) is used for a standard comparison. In this process, the yarn is led across a heated plate and through a twisting head such that twist backs up along the yarn in contact with the heated plate, the yarn being heat-set in a twisted condition, the yarn then cools and untwists as it passes through the twister head and is wound up. The crimp index is the difference in length of a treated yarn sample in the crimped state (L under a tension of 5.0 milligrams per denier and in the extended state (L under a load of 100 milligrams per denier expressed as percent of the extended length. It is determined as follows:

A 5,000 denier skein is prepared by winding on a creel under a tension of 0.1 gram per denier (based on textured yarn denier under 0.1 g.p.d. tension). The textured skein is conditioned by hanging a 25 gm. metal weight on the skein and suspending the skein with the weight attached in boiling water for 15 minutes. The skein is permitted to air dry while under the same load. The skein length is then measured under the same 25 gram load (crimped length, L and then under a 500 gram load (extended length, L Percent crimp index is LEV-L0 XIOO Spinning tension on the filaments is measured on the quenched filaments prior to contact with any surfaces such as guide pins or finish roll applicators. It is measured in a conventional manner using a yarn tensiometer such as a Type R1092 of Rothschild Instruments, Zurich, Switzerland. Since the filaments at the point of measurement contain no surface lubricant (finish), frictional problems due to filament contact with the tensiometer can be avoided by spraying a lubricant, such as a silicone oil, onto the moving filaments immediately prior to contact with the tensiometer measuring surfaces. Calculation of tension in grams per denier (g.p.d.) is based on the yarn denier after quenching and prior to drawing.

The spinning tension is preferably within the range of about 0.05-0.25 g.p.d. Lower tensions on the filaments in the spinning zone are generally impractical while higher tensions are undesirably detrimental to fiber performance in textile processing, for example, in yarn response to false-twist texturing processes. The higher the spinning tension, the poorer the response as reflected in the textured yarn Crimp Index.

The tension may be regulated, for example, by increasing the spinning temperature, altering the spinneret orifice dimensions (smaller orifices reduce the tension) and by increasing the temperature of the nonoxidizing atmosphere in the spinning zone. As the spinning speed is increased, the spinning tension increase and adjustments must be made as described above to keep the tension below the prescribed limit.

The quenched filaments are drawn to develop suificient molecular orientation and give the desired physical properties such as tenacity and elongation. The quenched filaments may be drawn in any conventional manner either in one or more stages with or without the addition of heat. They are drawn from about 1.2 to 2.0x (times their original length). A draw of at least about 1.2 is required since sufficient molecular orientation is not produced in the spun filaments, under the specified spinning tension. With draw ratios in excess of about 2.0x, elongation decreases to such an extent that the fibers are unsuitable for use under normal textile processing conditions.

Drawn yarn annealing temperatures (temperature of the annealing rolls) of 140 to 180 C. are used. When temperatures less than 140 C. are employed, it is found that the processed yarn possesses undesirably high shrinkage.

For preferred durability the polymers of this invention should have a realtive viscosity of at least about 45. Under otherwise constant spinning conditions, an increase in relative viscosity results in an increase in spinning tension.

The polymers employed in this invention are prepared from PACM having a trans-trans isomer content of at least about 45% and preferably at least about 60%. For textile applications the isomer content is preferably from about 60 to 80%. Higher trans trans isomer contents tend to make the polymers less tractable and more difiicult to spin under the prescribed low tensions at acceptably low spinning temperatures.

Spinning temperatures less than about 290 C. tend to increase unreasonably spinning tension and the pressure required for extruding the polymer through the spinneret. Temperatures above about 340 C. tend to produce an undesirable amount of thermal degradation.

EXAMPLE I This example demonstrates the improved performance of filaments spun at high speed when spinning tension is reduced.

Polymers of PACM containing 70% of the trans-trans isomer and dodecanedioic acid are melt-spun in a conventional manner using a spinneret containing 34 holes each 9 mils in diameter. The spinneret face is blanketed with steam from a radial diffuser equipped with a heated tail pipe about 12 cm. in length. The filaments are then quenched, a suitable lubricating finish is applied and they are drawn by means of two sets of draw rolls, the second set of rolls being heated and contained in a heated chest such that the yarn is annealed prior to being wound up..

EXAMPLE II A 65-denier, 34-filament yarn is prepared from polymer flake of the same composition as in Example I and having a relative viscosity of 50.8. The flake is dried prior to melt-spinning such that the relative viscosity increases by further polymerization during the spinning operation to give a final yarn relative viscosity of 80.8. As a result of this increase in viscosity from polymer flake to yarn, the end-group analysis of the polymer decreases from 62.6 carboxyl and 68.1 amine (equivalents per million grams of polymer) to 43.3 carboxyl and 48.5 amine endgroups. Symmetrical Y-shaped spinneret orifices are used to glve filaments having a symmetrical trilobal cross-sec- 4 tion having a modification ratio of 1.93, a tip radius ratio of 0.31 and an arm angle of 27 as described in U.S. Pat. No. 2,939,201 (Holland). The yarns are melt-spun and drawn in a conventional manner on a spinning apparatus of the type described in the drawing. The spinneret block temperature is 325 C. and that of the spinneret pack is 320 C. The steam temperature below the spinneret is 180 C. The spinning tension on the yarn is 0.0 8 gram per denier. The yarns are spun and quenched using a feed roll speed of 1300 y.p.m. and drawn in a single step using a first-stage draw roll speed of 2000 y.p.m. (1.54 draw ratio). The yarn is then annealed on the heated, secondstage draw rolls operating at a speed of 1867 y.p.m. and a temperature of 170 C. Yarn tensile properties are a tenacity of 3.9 grams per denier, 28% elongation and 37 grams per denier initial modulus. Crimp index of the yarn after false-twist texturing as described herein is 22.6%. The lower value in this case reflects the effect of filament cross-section on crimp index as compared to round yarns processed according to this mvention in Example I.

TABLE I Item A B C D Spinneret poly. temp. 314 314 314 294 Steam temp, C. 140 140 210 140 Tailpipe temp, C 80 80 Spinning (feed roll) speed, y.p.m 2, 740 2,740 2,740 3, 250 Draw Ratio:

1st stage l. 01 1. 01 1. 01 1. 01 Total 1. 24 1. 24 1. 25 l. 07 Anneal roll temp., 155 145 Windup speed, y.p.m 3, 450 3, 450 3, 450 3, 280 Spun yarn:

R." 57 60 62 62 Spinning tension (gum/spun d0l1l(}\') 0. 26 0. 30 0. 27 0. 48 Drawn yarn:

Denier 65 65 65 65 Tenacity, grams/den 4. 5 4. 85 4.65 3. 8 Elongation, percent- 32 27 28 35 Crimp index (percent) 40 29 39 18 What is claimed is:

1. A high-speed melt-spinning process for producing textile fibers having a tenacity of at least 3.0 grams per denier and an improved response to textile processing comprising extruding through a spinneret, filaments of a high molecular weight polymer consisting essentially of a polycarbonamide of bis(4-aminocyc1ohexyl)methane containing from 45 to 100% of the trans-trans isomer and dodecanedioic acid at a temperature of between 290 C. and 340 C., withdrawing the filaments from the spinneret at a speed of at least 1300 yards per minute and at a tension that is less than about 0.30 gram per denier, quenching the filaments, drawing said filaments from 1.2 to 2.0x and annealing the drawn filaments at a temperature of 140 C. to 180 C.

2. The process of claim 1 wherein the spinning tension is maintained within the range of 0.05 and 0.25 gram per denier.

3. The process of claim 1 wherein the filaments are extruded into a steam atmosphere.

References Cited UNITED STATES PATENTS 3,002,804 10/1961 Kilian 264181 3,118,012 1/1964 Kilian 18-8AX 3,251,181 5/1966 Breen et al. 57-140 3,361,859 1/1968 Cenzato 264210 3,414,646 12/1968 Pitzl 264176X 3,416,302 12/1968 Knospe 264168UX 3,423,809 1/1969 Schmitt 264103UX DONALD J. ARNOLD, Primary Examiner J. H. WOO, Assistant Examiner US. Cl. X.R. 264-176 may UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No i 23,305 Dated January 5, 1971 In'ventor(s) Tin Yam Au It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line I, after "19803" insert assignor to E. I. du Pont de Nemours and Company, Wilmington, Delaware,

a corporation of Delaware Signed and sealed this 27th day of April 1971.

(SEAL) Attest:

EDWARD M.FLE'I'CHER,J'R. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissioner of Patents 

